1. Field of the Invention
The present invention relates to a process for producing an optical element for use in displays such as a liquid crystal display. More particularly, the present invention relates to a method of patterning a film having a cholesteric order (i.e., a cholesteric film), and to an optical element including a cholesteric film patterned by the method.
2. Related Art
There have conventionally been proposed, as an optical element including a cholesteric film, a polarizing plate composed of laminates of a plurality of cholesteric liquid crystal layers having different chiral pitches (Japanese Laid-Open Patent Publications No. 271731/1996 and No. 264907/1999).
Such an optical element including a cholesteric film is often made in the following manner: a cholesteric film is formed on a large-sized glass substrate to obtain an original plate for optical elements, and, from this large-sized original plate, a plurality of optical elements are produced at one time. In this process, the glass substrate is notched in advance along lines corresponding to the peripheries of the optical elements to be finally produced, and the optical elements of the prescribed dimensions are separated from the original plate by exerting thereon a force needed. To ensure the separation of the optical elements from the original plate, it is desirable that those parts of the cholesteric film that correspond to the notches on the glass substrate also be removed beforehand.
Conventionally, cutting tools such as cutters are generally used for patterning of a cholesteric film in order to remove a part of the cholesteric film. However, if a cholesteric film is patterned by the use of cutting tools such as cutters, the patterned cholesteric film tend to have burrs or the like at the breaks in the films, and, in addition, become easy to come off.
We have made earnest studies on methods of patterning a cholesteric film; as a result, we have found that it is possible to efficiently and precisely pattern a cholesteric film by using laser light having a specific wavelength, or laser light containing, as its main component, a component circularly polarized in a specific direction.